As the cellular and wireless communication industries continue to define themselves, the promulgation of various standards and protocols continue to plague the industry. This plague along with the partitioning of the frequency spectrum has assured the need for dual-band, dual-mode radio transceivers into the foreseeable future.
Some manufacturers of radio telephone devices have succeeded in providing transceivers that are dual-mode (transceivers that support two or more protocols) and/or dual-band (transceivers that operate in multiple frequency ranges). However, these dual-band, dual-mode transceivers have distinct disadvantages which are addressed by the present invention. Early versions of dual-band transceivers included two transceivers that had the electronic components necessary to operate in both bands. This was the equivalent of taking two transceivers that operate in different bands and taping them back-to-back. The inefficiencies of component usage, power consumption, and the size were unacceptable.
In today's dual-band radio transceivers, the components of one band are shared to allow the transceiver to work in a second band. One key to today's technology is to use an oscillator (frequency source) that may be shifted between a first and a second frequency range. The frequency range of the frequency source is primarily a function of the band in which the transceiver is transmitting or receiving. However, prior art techniques have not fully reduced the number of oscillators required in a dual-band transceiver to the level achieved by the present invention. Thus, a first objective of the present invention is to reduce the component count, particularly the frequency sources and filters needed in a dual-band transceiver.
In addition to the use of a multiple band frequency source, a fixed second frequency source is utilized in some of the techniques provided today. In some prior art transmitters, the dual-band frequency source generates a first oscillation frequency and the second frequency source generates a second oscillation frequency. However, prior art fails to utilize the two oscillators for all the primary needs in both the transmitter and the receiver front and back-ends. Thus, it is another objective of the present invention to minimize the number of frequency sources required for the transmitter and the receiver front and back-ends.